1. Field of the Invention
This invention relates to an electronic flash system and more particularly to an indicating apparatus for an electronic flash system of the TTL light measurement type (1) to measure light which is emitted from an electronic flash unit and comes through the photograph taking lens of a camera and (2) to have the amount of illuminating light with which an object is to be photographed be controlled on the basis of the output of the light measurement.
2. Description of the Prior Art
Heretofore, electronic flash photographic systems of the above stated TTL light measurement type have been proposed and have been available in the market. Furthermore, there has also been proposed an electronic flash photographic unit (hereinafter called an electronic flash unit) of the TTL light measurement type which produces an illumination terminating signal and indicates when the signal is produced informing the photographer that a suitable amount of exposure is possible, i.e. for indicating that the object to be photographed is within a range in which the object is photographable.
However, in such a flash unit, the camera does not perform any stopping down action at the time of test light emission, that is, before a flash photographing operation is actually carried out. As a result, no information on the aperture position of the camera is introduced into the flash unit. Therefore, it has been impossible to indicate whether or not the object to be photographed is within the photographable range at the time of test light emission.
To obviate this shortcoming of conventional systems, a Japanese Patent Application, Laid-open No. 55-40413, has proposed an electronic flash system of the TTL light measurement type in which there is provided a member for setting the aperture of the camera and the diaphragm aperture of a photograph taking lens is stopped down to a predetermined aperture value at the time of test light emission in such a way as to indicate whether or not the object to be photographed is within the photographable range at the time of the light emission test. The method proposed, however, has been inconvenient because it necessitates a stopping down operation at the time of the light emission test.
It is an object of this invention to provide an indicating apparatus for an electronic flash system of the TTL light measurement type capable of eliminating the shortcomings of the prior art arrangements.
It is another object of the invention to provide an indicating apparatus of simple construction for an electronic flash system.
These and further objects, features and advantages of the invention will become apparent from the following detailed description thereof with the accompanying drawings.